Physical and mathematical methods are used to solve problems in the biomedical sciences, with emphasis on understanding phenomena in cell physiology. Special attention is being given to determining physical properties of structures formed from clathrin triskelions, the latter being large three-arm protein complexes that are involved in a major process by which eukaryotic cells take up materials from the extracellular milieu (receptor-mediated endocytosis). We developed a set of novel analytical an computational tools that relate shape variations in triskelions to underlying mechanical properties of the molecules. Information about triskelion energetics, obtained from electron micrographs, has been used in analysis of the sizes and shapes of reconstituted clathrin baskets. Relate studies have been directed towards understanding the mechanisms by which vesicles bleb from cell membranes, for which a mathematical theory presentl is being developed. Static and dynamic light scattering studies have been undertaken to measure shape transformations of clathrin triskelions when interacting with HSP70, which is a chaperone protein involved in the uncoating of endocytic vesicles. Related studies have been performed to determine the shapes and sizes of phospholipid vesicles formed under variou environmental conditions. Other projects include a mathematical analysis of data on the ligand-induced stiffening of neutrophils, and light and neutron scattering studies of structural transformations induced in micro tubule arrays and biopolymer gels by chemical and electrical stimuli.